This application claims priority to International Application No. PCT/GB99/04090 which was published on Jun. 29, 2000.
The invention relates to an arrangement of sensors for an autonomous vehicle, particularly but not exclusively for an autonomous vacuum cleaner.
An autonomous vehicle generally has a plurality of sensors for detecting obstacles in the path of the vehicle to prevent collision or accidents. While some autonomous vehicles can cope with undulating surfaces, they usually need to avoid any areas where there is a significant change in height, such as stairs where there is a danger that the machine can become stuck or fall, causing damage to the vehicle and to others. It is know to provide an autonomous vehicle with sensors that monitor the presence of a surface; these are often called xe2x80x9cdownlookingxe2x80x9d or xe2x80x9cdrop-offxe2x80x9d sensors.
A robotic cleaning device described in Patent Application WO 93/03399 has drop-off sensors at a forward edge of the cleaning device and is arranged to stop the drive motors when one of the dropoff sensors senses the absence of a surface beneath the cleaning device. U.S. Pat. No. 5,377,106 describes an unmanned cleaning vehicle with four drop-off sensors mounted on a bumper and side walls of the vehicle. The vehicle stops if any of the sensors senses an excessive distance between the sensor and the floor.
Safety regulations require that downlooking sensors should cause the vehicle to stop whenever the sensors detect the absence of a surface. This places severe constraints on flexibility of controlling the vehicle near to any places where these is a significant change in height. The present invention seeks to provide more flexibility in operating an autonomous vehicle under these conditions.
According to a first aspect of the invention, there is provided an autonomous vehicle comprising wheels for supporting the vehicle and for allowing the vehicle to traverse a surface, downward looking wheel sensors for sensing the presence of a surface in front of the whells, a further sensor at or near a leading edge of the vehicle for sensing the presence of a surface beneath the leading edge of the vehicle and a control apparatus for controlling movement of the vehicle, the control apparatus being arranged to permit movement of the vehicle when the leading edge sensor detects the absence of a surface beneath the leading edge of the vehicle, providing the wheel sensors indicate the presence of a surface adjacent the wheel. This has the advantage of allowing more flexibility in controlling movement of the cleaning device.
Preferably, the vehicle is arranged to operate so that when the leading edge sensor detects the absence of a surface beneath the leading edge of the vehicle, the vehicle performs an edge following routine. The edge following routine can be a zig-zag movement along the edge, or it can use a further downloading sensor which senses the presence of a surface adjacent a side edge of the vehicle.
Further aspects of the invention provide a method of operating an autonomous vehicle, software for performing a method of controlling operation of an autonomous vehicle and a control apparatus for controlling operation of an autonomous vehicle.
An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, wherein: